<div id="header">
<form action="" method="post" name="frmSearch" onSubmit="return SearchGoogle();" id="frmSearch">
    <div id="btnSearch"><input type="image" name="btnSearch" src="images/btnSearch.png" /></div>
    <div id="txtSearch" style="background:url(images/txtSearch.png);"><input type="text" name="txtSearch" value="" id="key_search" style="background:none; border:none;" /></div>
</form>
<script type="text/javascript">
    function SearchGoogle(){
    var key = document.getElementById("key_search").value;
    var site = document.domain;
    var qs = key + "+site:" + site;
    var url = "http://www.google.com.vn/#sclient=psy-ab&hl=vi&site=&source=hp&q=" + qs + "&pbx=1&oq=" + qs + "&aq=f&aqi=&aql=1&gs_sm=e";
    window.open(url, '_blank');
    return false;
}
</script></div>